In some production systems, for instance the manufacture of very large scale integrated circuits (VLSIC's), it is standard to work in an atmosphere of inert gas. It is essential, due to the tiny size and potential corrodibility of the parts, that this process gas be extremely pure, in fact any impurities such as oxygen or volatile hydrocarbons must be reduced to the ppb range where they are in fact barely measurable. Many other processes demand that the gas being used--whether an inert gas such as argon or xenon or a reactive gas such as hydrogen--be extraordinarily pure.
A variety of purification systems are available commercially. In some, as for example those marketed by Labclear, Inc. and Semi-Gas Systems, Inc., in-line cartridges filled with molecular-sieve or polymeric-resin absorber material are connected in series in the gas feed lines. These systems have straight-through flow and are intended generally for ambient temperature operation. Such systems do not reduce nitrogen or hydrogen to ppb levels and require either large quantities of absorber material or exceedingly low flow rates to reduce CO.sub.2, CH.sub.4, and other hydrocarbons to the ppb level.
In comparable purification systems, process gas is passed over metallic getter materials. Cu--CuO is used as an oxygen purifier by Supelco, Ti sponge by R. D. Mathis, and a Zr--V--Fe alloy by SAES Getters S.p.A. When heated the latter two materials are effective getters for all reactive gas species, including N.sub.2, CO.sub.2, and CH.sub.4. However, existing purifier systems have bulky heaters, flanges, or inefficient gas-solid contacting. The Ti systems also are disadvantaged by higher operating temperatures required for purification.